1. Field of the Invention
The present invention relates to a duplex web roll winding and splicing apparatus for continuously winding a moving web and also for splicing and transferring the web to a new core without stopping movement of the web. In particular, this invention relates to an apparatus and method for continuously winding and splicing a moving web onto a successive series of cores without causing a fold-back or wrinkling of the web.
2. Background of the Related Art
Many commercial and industrial laminating, coating and film processing operations are conducted on high speed web handling equipment which operate continuously for long periods of time. Paper converting is one example of such an operation. Numerous kinds of plastic film and thin foils are also processed in this manner. At the end of the processing line the web is wound lengthwise into a large roll of material commonly referred to in the trade as a parent roll, mill roll or finish roll. In the processing of web materials, it is inefficient to stop the entire operation each time an individual roll of material needs to be changed. For this reason, various types of winding and rewinding devices have been developed for cutting and transferring a moving web onto a new core so that successive rolls of material may be continuously wound without interrupting the web processing operation.
One such rewind device, commonly referred to in the trade as either a turnover rewind stand or turret rewinder, is disclosed in U.S. Pat. No. 3,529,785. A turnover rewind stand is comprised of a pair of rotatable spindles or cores mounted on opposite ends of a turret. During normal operation, one core is positioned close to the web processing line for rewinding the web, while the other core on the opposite end of the turret is positioned away from the web processing line. By revolving or "turning over" the turret, the spindle containing a fully wound roll of web material is moved away from the rewinding position and a new core is simultaneously moved into the rewinding position. The splice is accomplished by placing the moving web into contact with the new core, which is covered with an adhesive, and then severing the web with a knife at a point which is normally downstream from the new core. The web sticks to the new core and thereafter the web is rewound onto the new core. The finished roll, which is now positioned away from the processing line, may be removed and another new core put in its place. This process, referred to in the trade as splicing the web "on the fly," may be repeated over and over in order to rewind a number of rolls successively for as long as the web processing line is in operation.
The splicing step described above involves cutting the web at a point which is downstream from the new core, which causes a portion of the web to fold-back on itself on the new core when the splice is performed. This fold-back results in a double thickness of the web and wrinkling of the web at the core which is undesirable. While the affects of the fold-back may be alleviated after a number of revolutions on the new core, the fold-back nonetheless produces a significant amount of waste material.
Several devices have been developed in an effort to provide a "no-fold-back" transfer of a moving web. The applicant's prior U.S. Pat. No. 5,368,253, entitled Continuous Rewind With No-Fold-Back Splicer, discloses one such device. The device disclosed in the '253 patent uses a perforated knife to cut the web at a point which is upstream from the new core. Gaps in the perforated knife leave a set of tabs which hold the web together until the cut seam reaches the new core. At that point, the "new" leading edge of the web becomes bonded to a strip of adhesive on the new core. The adhesive bond overpowers the tabs thereby causing the tabs to break. As a result, the tail of the web continues on its normal path to become rewound about the old finish roll, while the new leading edge becomes bonded to the new core. The splice is made without the usual fold-back encountered in conventional splicing operation.
The applicant's prior U.S. Pat. No. 5,823,461 entitled No-Fold-Back Splicer with Electrostatic Web Transfer Device discloses another example of a splicing device for a rewinder which produces a no-fold-back splice. On the device disclosed in the '461 patent the web is fed through a first nip point formed by an introducer roll and a cushioned anvil roll, and then through a second nip point formed by the cushioned anvil roll and the new core. An electrostatic charging bar positioned downstream from the first nip point emits an electrostatic charge onto the web to temporarily adhere it to the cushioned anvil roll. A rotatable cutting knife which is cooperatively engageable with the cushioned anvil roll cuts the web at a point downstream from the electrostatic charging bar but upstream from the new core thereby forming a tail and a new leading edge. The tail continues to be rewound about a finish roll. Because the new leading edge of the web has been electrostatically charged it remains stuck to the cushioned anvil roll until it reaches the new core. At that point, adhesive on the new core peels the new leading edge of the web off of the cushioned anvil roll and affixes it onto the new core. The web is thereafter rewound about the new core.
However, the two devices disclosed in the '253 and '461 patents are both designed for use on or in connection with a turret style rewinder. As mentioned, a turret style rewinder includes a first core mounted on one end of the turret arm, and a second core mounted on the opposite end of the turret arm. The rewinding operation is normally conducted on the core that is located in the position closest to the end of the web processing line. In preparation for the splice, the turret arm is rotated so that the first core, which is ready to be finished and removed from the rewind stand, is rotated away from the web processing line and the new core is simultaneously rotated into position to take over the rewinding operation. (See, e.g., U.S. Pat. No. 5,368,253, FIGS. 1 and 2 and specification column 4, lines 30-50, and U.S. Pat. No. 5,823,461, FIG. 1 and specification column 3, line 66 to column 4, line 18.) During the period that the finish roll is positioned away from the web processing line, yet prior to splicing, the web must traverse a substantial distance while unsupported by any rollers or other structural components of the web processing equipment. Some web materials, such as very light weight films and foils, may become stretched, wrinkled, warped or might even tear while traveling over the unsupported area. Of course, such defects and imperfections are undesirable and oftentimes entirely unacceptable, resulting in the production of undue amounts of waste material. In order to avoid creating such defects and imperfections, delicate materials such as extremely thin films and foils are often applied to a rewind core with a lay-on roll. A lay-on roll is quite simply a roll that is located in close proximity to the rewind core. The lay-on roll and rewind core are close enough together to form either a nip point, or at most a short gap between the lay-on roll and rewind core. The lay-on roll therefore essentially applies the web directly onto the rewind core. As mentioned, conventional turret rewinders produce too large of a space for the web to cross over during the splicing step to be used in such applications.
Other examples of no-fold-back splicers include the device disclosed in U.S. Pat. No. 4,422,528 to Richard S. Tetro (The Black Clawson Company) and another device produced by IMD Corporation, which uses a vacuum to transfer the web to the new core during the splicing operation. However, both devices are extremely complex and are severely limited to handling a narrow range of materials and web speeds.